With people's standard of living gradually improved, cars have become the most important means of transport in people's daily lives. More and more people buy cars, but the numbers of road accidents are also on the rise, especially rear-end collisions accounting for a relatively large proportion of accidents, often causing heavy casualties and economic losses.
Most rear-end collisions are generally caused by, after a front vehicle involved in an accident or breakdown, advance-warning not being promptly given, which cause following vehicles to have rear-end collisions to create more and severer traffic accidents. The rear-end collisions are also caused by the poor visibility and closeness to the accident scene of the warning equipment of the vehicle involved in the accident, the following vehicles do not have sufficient response time or response distance, causing severer traffic accidents. Thus, as required by transportation authorities, after a road accident, an advance-warning device must be used to warn the following vehicles, at a distance of 100˜250 meters.
Currently, an advance-warning device is often a triangle sign placed in car trunk. The triangle sign typically has a reflective region. When the vehicle is breakdown or in accident, the triangle sign is placed in the rear of the vehicle to warn the oncoming cars from behind. For example, on a highway with 110 km/h speed limit, when a vehicle breaks down at night, the driver needs to get out of the vehicle and takes the warning triangle sign out of the trunk, walks at least a safe distance behind the breakdown vehicle, and then places the warning triangle sign to warn the oncoming vehicles. Afterward, the driver needs to retrieve the warning triangle sign.
According to the traffic regulations, the safe distance of 250 meters, which means that the driver is required to walking back and forth twice, at least 1000 meters. Due to human laziness, under the on-site emergency and hazardous situation, people usually do not follow the regulations to place the triangle sign. Even when people follow the regulation to place the triangle sign, it may take a long time to place it, i.e., a slow placement. The study showed that: the probability of occurrence of the secondary accident, or two or more car rear-end accident after more than 10 seconds, is proportional to the time for placing the triangle sign. That is, the shorter the placement time, the smaller the probability of occurrence of the secondary accident.
In addition, when the driver walk on the roadway by foot to place the car triangle sign, especially at night, rain, fog, snow and other inclement weather without clear line of sight, it may lead to more severer traffic accidents, not to mention traffic accidents occurred under these weather conditions account 82.5% of total accidents. Furthermore, when the existing triangle signs are used under the rain and fog weather or at night, their visibility is very low, the warning distance is short, and the effect is not desired.